1. Technical Field
The present invention relates to a multi-layered structure forming method using a liquid droplet ejecting apparatus and more particularly to a multi-layered structure forming method suitable for manufacturing a wiring substrate and an electronic apparatus.
2. Related Art
A method of manufacturing a wiring substrate or a circuit board by use of an additive process with a printing method has attracted attention. This is because cost for the additive process is lower than that for a method of manufacturing a wiring substrate or a circuit board by repeating a thin film coating process and a photolithography process.
A technique of forming a conductive pattern by use of an inkjet method is known as one technique used for the additive process (for example, see Japanese Unexamined Patent Application Publication No. 2004-6578).
Japanese Unexamined Patent Application Publication No. 2004-6578 is an example of the related art.
However, when a plurality of resin layers are stacked using an inkjet method, stress may remain in the interface between a base layer and a layer covering the base layer. As a result, when external impact or heat is applied, cracks may be generated in the interface.
When an insulating layer having a via hole is provided using an inkjet method, a first insulating pattern triming the via hole and a second insulating pattern surrounding the first insulating pattern are often formed individually. Specifically, the first insulating pattern is formed to trim the shape of the via hole and then the second insulating pattern is formed to surround the first insulating pattern. This is because the outline of the via hole is clearer and the insulating layer can be formed widely. However, in such a method, stress may remain in the interface between the insulating patterns individually formed, due to the hardening contraction at the time of hardening the insulating patterns. As a result, when external impact or heat is applied, cracks may be generated in the interface.